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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v5 for 4.5] xen/arm: Correctly support WARN_ON
Currently the hypervisor will hang if it hits a WARN_ON.
The implementation uses an undefined instruction, made ourself because ARM
don't provide one, to implement BUG/ASSERT/WARN_ON, and sets up the
different tables (one for each type) which contain useful information.
This is based on the x86 implementation (include/asm-x86/bug.h). Unfortunately
the structure can't be shared because many ARM{32,64} gcc versions doesn't
correctly support %c. The support for executing a function in an exception
handler
is also keep unimplemented on ARM. Therefore, dump_execution_state is
implemented as WARN()
The current opcode used to go in exception mode may not be undefined on ARM64.
Use the instruction "brk" to generate a software debug exception.
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
This is a bug fix for Xen 4.5. It make WARN_ON working correctly
when it has been hit in the hypervisor.
Changes in v5:
- Fix typoes in the commit message.
Changes in v4:
- Check if the regs represents an hyp mode view rather than
checking HCR_EL2.TGE and MDCR_EL2.TDE.
Changes in v3:
- Typoes
- Uppercase first letter of each word of do_unexpected_trap
- Check that PC is effectly a multiple of 4 for ARM32
- Make BUG_ON/WARN/ASSERT working during early boot (i.e when a
current is not correctly set)
- Check that HCR.EL2.TGE and MDCR_EL2.TDE are not set
- Replace regs->pc by the local variable pc in arch/arm/arm32/traps.c
Changes in v2:
- Missing static in do_bug_frame prototype
- Add support for ARM64 by using the instruction brk
- Implement dump_execution_state as WARN
---
xen/arch/arm/arm32/traps.c | 23 +++++++++
xen/arch/arm/traps.c | 107 ++++++++++++++++++++++++++++++++++++++-
xen/arch/arm/xen.lds.S | 8 +++
xen/include/asm-arm/arm32/bug.h | 13 +++++
xen/include/asm-arm/arm64/bug.h | 10 ++++
xen/include/asm-arm/bug.h | 77 ++++++++++++++++++++++++++--
xen/include/asm-arm/debugger.h | 2 +-
xen/include/asm-arm/processor.h | 18 ++++++-
8 files changed, 252 insertions(+), 6 deletions(-)
create mode 100644 xen/include/asm-arm/arm32/bug.h
create mode 100644 xen/include/asm-arm/arm64/bug.h
diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index ff0b945..f8cf864 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -18,6 +18,7 @@
#include <xen/config.h>
#include <xen/lib.h>
+#include <xen/kernel.h>
#include <public/xen.h>
@@ -25,6 +26,28 @@
asmlinkage void do_trap_undefined_instruction(struct cpu_user_regs *regs)
{
+ uint32_t pc = regs->pc;
+ uint32_t instr;
+
+ if ( !is_kernel_text(pc) &&
+ (system_state >= SYS_STATE_active || !is_kernel_inittext(pc)) )
+ goto die;
+
+ /* PC should be always a multiple of 4, as Xen is using ARM instruction
set */
+ if ( regs->pc & 0x3 )
+ goto die;
+
+ instr = *((uint32_t *)pc);
+ if ( instr != BUG_OPCODE )
+ goto die;
+
+ if ( do_bug_frame(regs, pc) )
+ goto die;
+
+ regs->pc += 4;
+ return;
+
+die:
do_unexpected_trap("Undefined Instruction", regs);
}
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 4b4b4e0..f6fc8f8 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -32,6 +32,7 @@
#include <xen/domain_page.h>
#include <public/sched.h>
#include <public/xen.h>
+#include <asm/debugger.h>
#include <asm/event.h>
#include <asm/regs.h>
#include <asm/cpregs.h>
@@ -1050,6 +1051,102 @@ void do_unexpected_trap(const char *msg, struct
cpu_user_regs *regs)
panic("CPU%d: Unexpected Trap: %s\n", smp_processor_id(), msg);
}
+int do_bug_frame(struct cpu_user_regs *regs, vaddr_t pc)
+{
+ const struct bug_frame *bug;
+ const char *prefix = "", *filename, *predicate;
+ unsigned long fixup;
+ int id, lineno;
+ static const struct bug_frame *const stop_frames[] = {
+ __stop_bug_frames_0,
+ __stop_bug_frames_1,
+ __stop_bug_frames_2,
+ NULL
+ };
+
+ for ( bug = __start_bug_frames, id = 0; stop_frames[id]; ++bug )
+ {
+ while ( unlikely(bug == stop_frames[id]) )
+ ++id;
+
+ if ( ((vaddr_t)bug_loc(bug)) == pc )
+ break;
+ }
+
+ if ( !stop_frames[id] )
+ return -ENOENT;
+
+ /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
+ filename = bug_file(bug);
+ if ( !is_kernel(filename) )
+ return -EINVAL;
+ fixup = strlen(filename);
+ if ( fixup > 50 )
+ {
+ filename += fixup - 47;
+ prefix = "...";
+ }
+ lineno = bug_line(bug);
+
+ switch ( id )
+ {
+ case BUGFRAME_warn:
+ printk("Xen WARN at %s%s:%d\n", prefix, filename, lineno);
+ show_execution_state(regs);
+ return 0;
+
+ case BUGFRAME_bug:
+ printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
+
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return 0;
+
+ show_execution_state(regs);
+ panic("Xen BUG at %s%s:%d", prefix, filename, lineno);
+
+ case BUGFRAME_assert:
+ /* ASSERT: decode the predicate string pointer. */
+ predicate = bug_msg(bug);
+ if ( !is_kernel(predicate) )
+ predicate = "<unknown>";
+
+ printk("Assertion '%s' failed at %s%s:%d\n",
+ predicate, prefix, filename, lineno);
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return 0;
+ show_execution_state(regs);
+ panic("Assertion '%s' failed at %s%s:%d",
+ predicate, prefix, filename, lineno);
+ }
+
+ return -EINVAL;
+}
+
+#ifdef CONFIG_ARM_64
+static void do_trap_brk(struct cpu_user_regs *regs, union hsr hsr)
+{
+ /* HCR_EL2.TGE and MDCR_EL2.TDE are not set so we never receive
+ * software breakpoint exception for EL1 and EL0 here.
+ */
+ BUG_ON(!hyp_mode(regs));
+
+ switch (hsr.brk.comment)
+ {
+ case BRK_BUG_FRAME:
+ if ( do_bug_frame(regs, regs->pc) )
+ goto die;
+
+ regs->pc += 4;
+
+ break;
+
+ default:
+die:
+ do_unexpected_trap("Undefined Breakpoint Value", regs);
+ }
+}
+#endif
+
typedef register_t (*arm_hypercall_fn_t)(
register_t, register_t, register_t, register_t, register_t);
@@ -1921,7 +2018,8 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs
*regs)
* correctly (See XSA-102). Until that is resolved we treat any
* trap from 32-bit userspace on 64-bit kernel as undefined.
*/
- if ( is_64bit_domain(current->domain) && psr_mode_is_32bit(regs->cpsr) )
+ if ( !hyp_mode(regs) && is_64bit_domain(current->domain) &&
+ psr_mode_is_32bit(regs->cpsr) )
{
inject_undef_exception(regs, hsr.len);
return;
@@ -2006,6 +2104,13 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs
*regs)
case HSR_EC_DATA_ABORT_LOWER_EL:
do_trap_data_abort_guest(regs, hsr);
break;
+
+#ifdef CONFIG_ARM_64
+ case HSR_EC_BRK:
+ do_trap_brk(regs, hsr);
+ break;
+#endif
+
default:
bad_trap:
printk("Hypervisor Trap. HSR=0x%x EC=0x%x IL=%x
Syndrome=0x%"PRIx32"\n",
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 079e085..cca1d8c 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -40,6 +40,14 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
.rodata : {
_srodata = .; /* Read-only data */
+ /* Bug frames table */
+ __start_bug_frames = .;
+ *(.bug_frames.0)
+ __stop_bug_frames_0 = .;
+ *(.bug_frames.1)
+ __stop_bug_frames_1 = .;
+ *(.bug_frames.2)
+ __stop_bug_frames_2 = .;
*(.rodata)
*(.rodata.*)
_erodata = .; /* End of read-only data */
diff --git a/xen/include/asm-arm/arm32/bug.h b/xen/include/asm-arm/arm32/bug.h
new file mode 100644
index 0000000..155b420
--- /dev/null
+++ b/xen/include/asm-arm/arm32/bug.h
@@ -0,0 +1,13 @@
+#ifndef __ARM_ARM32_BUG_H__
+#define __ARM_ARM32_BUG_H__
+
+#include <xen/stringify.h>
+
+/* ARMv7 provides a list of undefined opcode (see A8.8.247 DDI 0406C.b)
+ * Use one them encoding A1 to go in exception mode
+ */
+#define BUG_OPCODE 0xe7f00f0
+
+#define BUG_INSTR ".word " __stringify(BUG_OPCODE)
+
+#endif /* __ARM_ARM32_BUG_H__ */
diff --git a/xen/include/asm-arm/arm64/bug.h b/xen/include/asm-arm/arm64/bug.h
new file mode 100644
index 0000000..42b0e4f
--- /dev/null
+++ b/xen/include/asm-arm/arm64/bug.h
@@ -0,0 +1,10 @@
+#ifndef __ARM_ARM64_BUG_H__
+#define __ARM_ARM64_BUG_H__
+
+#include <xen/stringify.h>
+
+#define BRK_BUG_FRAME 1
+
+#define BUG_INSTR "brk " __stringify(BRK_BUG_FRAME)
+
+#endif /* __ARM_ARM64_BUG_H__ */
diff --git a/xen/include/asm-arm/bug.h b/xen/include/asm-arm/bug.h
index 458c818..ab9e811 100644
--- a/xen/include/asm-arm/bug.h
+++ b/xen/include/asm-arm/bug.h
@@ -1,10 +1,81 @@
#ifndef __ARM_BUG_H__
#define __ARM_BUG_H__
-#define BUG() __bug(__FILE__, __LINE__)
-#define WARN() __warn(__FILE__, __LINE__)
+#include <asm/processor.h>
-#endif /* __X86_BUG_H__ */
+#if defined(CONFIG_ARM_32)
+# include <asm/arm32/bug.h>
+#elif defined(CONFIG_ARM_64)
+# include <asm/arm64/bug.h>
+#else
+# error "unknown ARM variant"
+#endif
+
+#define BUG_DISP_WIDTH 24
+#define BUG_LINE_LO_WIDTH (31 - BUG_DISP_WIDTH)
+#define BUG_LINE_HI_WIDTH (31 - BUG_DISP_WIDTH)
+
+struct bug_frame {
+ signed int loc_disp; /* Relative address to the bug address */
+ signed int file_disp; /* Relative address to the filename */
+ signed int msg_disp; /* Relative address to the predicate (for ASSERT)
*/
+ uint16_t line; /* Line number */
+ uint32_t pad0:16; /* Padding for 8-bytes align */
+};
+
+#define bug_loc(b) ((const void *)(b) + (b)->loc_disp)
+#define bug_file(b) ((const void *)(b) + (b)->file_disp);
+#define bug_line(b) ((b)->line)
+#define bug_msg(b) ((const char *)(b) + (b)->msg_disp)
+
+#define BUGFRAME_warn 0
+#define BUGFRAME_bug 1
+#define BUGFRAME_assert 2
+
+/* Many versions of GCC doesn't support the asm %c parameter which would
+ * be preferable to this unpleasantness. We use mergeable string
+ * sections to avoid multiple copies of the string appearing in the
+ * Xen image.
+ */
+#define BUG_FRAME(type, line, file, has_msg, msg) do { \
+ BUILD_BUG_ON((line) >> 16); \
+ asm ("1:"BUG_INSTR"\n" \
+ ".pushsection .rodata.str, \"aMS\", %progbits, 1\n" \
+ "2:\t.asciz " __stringify(file) "\n" \
+ "3:\n" \
+ ".if " #has_msg "\n" \
+ "\t.asciz " #msg "\n" \
+ ".endif\n" \
+ ".popsection\n" \
+ ".pushsection .bug_frames." __stringify(type) ", \"a\", %progbits\n"\
+ "4:\n" \
+ ".long (1b - 4b)\n" \
+ ".long (2b - 4b)\n" \
+ ".long (3b - 4b)\n" \
+ ".hword " __stringify(line) ", 0\n" \
+ ".popsection"); \
+} while (0)
+
+#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, "")
+
+#define BUG() do { \
+ BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 0, ""); \
+ unreachable(); \
+} while (0)
+
+#define assert_failed(msg) do { \
+ BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg); \
+ unreachable(); \
+} while (0)
+
+extern const struct bug_frame __start_bug_frames[],
+ __stop_bug_frames_0[],
+ __stop_bug_frames_1[],
+ __stop_bug_frames_2[];
+
+int do_bug_frame(struct cpu_user_regs *regs, vaddr_t pc);
+
+#endif /* __ARM_BUG_H__ */
/*
* Local variables:
* mode: C
diff --git a/xen/include/asm-arm/debugger.h b/xen/include/asm-arm/debugger.h
index 916860b..ac776ef 100644
--- a/xen/include/asm-arm/debugger.h
+++ b/xen/include/asm-arm/debugger.h
@@ -1,7 +1,7 @@
#ifndef __ARM_DEBUGGER_H__
#define __ARM_DEBUGGER_H__
-#define debugger_trap_fatal(v, r) ((void) 0)
+#define debugger_trap_fatal(v, r) (0)
#define debugger_trap_immediate() ((void) 0)
#endif /* __ARM_DEBUGGER_H__ */
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 07a421c..e719c26 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -3,6 +3,7 @@
#include <asm/cpregs.h>
#include <asm/sysregs.h>
+#include <public/arch-arm.h>
/* MIDR Main ID Register */
#define MIDR_MASK 0xff0ffff0
@@ -179,6 +180,7 @@
#define HDCR_TDRA (_AC(1,U)<<11) /* Trap Debug ROM access */
#define HDCR_TDOSA (_AC(1,U)<<10) /* Trap Debug-OS-related
register access */
#define HDCR_TDA (_AC(1,U)<<9) /* Trap Debug Access */
+#define HDCR_TDE (_AC(1,U)<<8) /* Route Soft Debug exceptions
from EL1/EL1 to EL2 */
#define HDCR_TPM (_AC(1,U)<<6) /* Trap Performance Monitors
accesses */
#define HDCR_TPMCR (_AC(1,U)<<5) /* Trap PMCR accesses */
@@ -205,6 +207,9 @@
#define HSR_EC_INSTR_ABORT_CURR_EL 0x21
#define HSR_EC_DATA_ABORT_LOWER_EL 0x24
#define HSR_EC_DATA_ABORT_CURR_EL 0x25
+#ifdef CONFIG_ARM_64
+#define HSR_EC_BRK 0x3c
+#endif
/* FSR format, common */
#define FSR_LPAE (_AC(1,UL)<<9)
@@ -452,6 +457,17 @@ union hsr {
unsigned long len:1; /* Instruction length */
unsigned long ec:6; /* Exception Class */
} dabt; /* HSR_EC_DATA_ABORT_* */
+
+#ifdef CONFIG_ARM_64
+ struct hsr_brk {
+ unsigned long comment:16; /* Comment */
+ unsigned long res0:9;
+ unsigned long len:1; /* Instruction length */
+ unsigned long ec:6; /* Exception Class */
+ } brk;
+#endif
+
+
};
#endif
@@ -583,7 +599,7 @@ void panic_PAR(uint64_t par);
void show_execution_state(struct cpu_user_regs *regs);
void show_registers(struct cpu_user_regs *regs);
//#define dump_execution_state() run_in_exception_handler(show_execution_state)
-#define dump_execution_state() asm volatile (".word 0xe7f000f0\n"); /* XXX */
+#define dump_execution_state() WARN()
#define cpu_relax() barrier() /* Could yield? */
--
1.7.10.4
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